The following invention relates to a flex circuit for coupling the drive electronics, located outside of an electric motor, to the stator coils of an electric motor, and in particular relates to a one piece flex circuit for accomplishing this objective.
Disk drive spindle motors are motors that are driven by energizing the stator coils of the motor with electric currents that are supplied to the coils from electronic drivers outboard of the motor. One problem in the design of such devices is that of providing a connection for coupling the drive electronics to the stator coils to supply the currents necessary to drive the motors. This is essentially a fabrication problem where the object is to provide this connection in a way that reduces the number of process steps needed to manufacture the motor. These connections, which are usually made by running wires through the motor and by soldering those wires to the stator coils, are labor intensive and frequently prone to failure.
In the past motors have employed flex circuits as transmission media for coupling outboard electronic drivers to the coils of a motor. One such scheme is shown in Tanaka et al. U.S. Pat. No. 5,256,922. Tanaka employs a flex circuit consisting of a flexible PC film bearing circuit runs which is threaded through the motor and includes a land portion and a lead portion. The land portion which extends through an opening in the housing to the outside (referred to in Tanaka et al. as the lead portion) is a thin, flat, belt-like strip which carries connectors from the region adjacent the stator coils to a location outside of the motor. The lead portion (referred to in Tanaka et al. as the land portion) includes a plurality of arms or the like encircling the spindle in which each arm provides a number of spaced-apart solder points for connection to wires leading to the stator coils. The land portion (Tanaka's lead portion) extends generally along the coils through a slot in the base of the motor to some point outside the motor. The problem with this design is the difficulty of soldering wires from the coils to the lead portions (Tanaka's land portions) of the flex circuit at spaced locations around the spindle. The lead portions (Tanaka's land portions) must be wrapped around the spindle which is difficult to automate. In addition, the arms of the lead portion (Tanaka's land portion) give the circuit a shape which cannot easily be threaded through the motor.
Another type of prior art flex circuit is illustrated in FIGS. 1 and 1A. This design is manufactured by Seagate Technology. It overcomes the problem of the arm members of the aforementioned U.S. Pat. No. 5,256,922 by concentrating the solder leads adjacent one another on a narrow lead strip of PC material. As shown in FIG. 1 a piece of base flex material 1 includes bond pads 2 which are connected to solder leads 3. The base flex portion of FIG. 1, however, must be connected to the shaft flex portion 4 as shown in FIG. 1A. The shaft flex portion 4 includes solder points 5 which are intended to be connected to solder pads 3 on the base flex material 1. In this design the solder winding leads are all located adjacent one another at the end of the flex circuit 4 so that the operation of soldering the stator coils to the winding leads on the flex circuit 4 is simplified. The problem with the construction of FIGS. 1 and 1A is that an additional soldering operation must be performed. The pads 5 on the shaft flex circuit must be soldered to the pads 3 on the base flex circuit. This is an additional manufacturing step which requires the use of solder points which are prone to breakage.